Association of Low-Grade Hemolysis With Early Tubular Injury in Non-anemic Adults

Low-grade hemolysis may occur in individuals with normal hemoglobin levels and contribute to oxidative stress and early renal injury. Serum lactate dehydrogenase (LDH), although a non-specific biomarker, may serve as a surrogate marker of potential low-grade hemolysis or cellular injury. In contrast, urinary neutrophil gelatinase-associated lipocalin (uNGAL) is a sensitive biomarker of early renal tubular injury. This study examined the association between elevated LDH levels and early tubular injury in non-anemic adults.

A cross-sectional analytical study was conducted among 450 non-anemic adults from tertiary care hospitals and outpatient departments (OPDs). Participants were classified into the elevated-LDH and normal-LDH groups. A structured proforma was used to gather demographic and clinical data. Hemoglobin, serum LDH, and creatinine were measured in blood, and uNGAL was measured in urine. Spearman's correlation, the Mann-Whitney U test, and multiple linear regression were performed to assess the independent association between serum LDH and uNGAL after adjusting for potential confounding factors.

Among the participants, 235 (52.2%) were male, and 104 (23.1%) were in the 36-45-year age group. There was a weak-to-moderate positive correlation between serum LDH and urinary NGAL (ρ = 0.350, p < 0.001). The urinary NGAL level was significantly higher in individuals with elevated LDH (220 ± 50 ng/mL) compared with those with normal LDH (150 ± 40 ng/mL) (p < 0.001). After adjustment for the confounding variables, serum LDH was independently associated with the uNGAL levels (B = 0.200, β = 0.220, p < 0.001).

An association was observed between elevated serum LDH and increased urinary NGAL concentrations in non-anemic adults, suggesting that elevated LDH levels may be associated with subclinical renal tubular stress even in the absence of clinically apparent anemia or kidney disease. Urinary NGAL could be a potential early biomarker of subclinical renal injury and a marker of the risk of renal dysfunction.